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Otto Piechowski
Pooh-Bah


Reged: 09/20/05

Loc: Lexington, KY
Re: Sending humans to Mars actually feasible? new [Re: Mister T]
      #5989064 - 07/25/13 07:09 AM

Well, thank you for dispelling that bit of science fiction (i.e. terraforming Mars).

Otto


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trw
member


Reged: 07/28/09

Re: Sending humans to Mars actually feasible? new [Re: Otto Piechowski]
      #5989274 - 07/25/13 10:27 AM

Where are we at present with the problems of muscle atrophy and bone decalcification taking place over long periods of zero G? Last I knew astronauts coming back from prolonged ISS and Mir stays,despite heavy exercise, were returning seriously debilitated and with bone loss that did not recover. Not a good prospect for a Mars mission.

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llanitedave
Humble Megalomaniac
*****

Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Sending humans to Mars actually feasible? new [Re: trw]
      #5989284 - 07/25/13 10:35 AM

I still can't see why there's no design there for a rotating habitat assembly to generate artificial gravity on long trips.

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Jarad
Postmaster
*****

Reged: 04/28/03

Loc: Atlanta, GA
Re: Sending humans to Mars actually feasible? new [Re: llanitedave]
      #5989361 - 07/25/13 11:16 AM

Several have been tossed around, including having 2 modules connected by a long tether spinning around a common center of mass. None have really been tested to make sure they are stable for the required duration.

Seems to me that it would make sense to design the next LEO space station to rotate and generate artificial gravity as a test bed.

Jarad


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Ravenous
sage


Reged: 11/14/09

Loc: UK
Re: Sending humans to Mars actually feasible? new [Re: Otto Piechowski]
      #5989543 - 07/25/13 01:14 PM

Quote:


Now, let us turn to the content of the second point you made when you wrote, “This forum is for discussion of science. Period. “





Oh dear. I was going to prepare one of those page-long irritating posts where I quote every one of your false assumptions and correct each in turn, but I dislike seeing those and out of respect for everyone else I felt it best not to do so. So I'll give you the short version.

The rules do not apply to you. You are a philosopher, an intelligent one at that, and can redefine words to mean whatever you wish in defence of your argument. Metaphysics and science are linked, metaphysics and religion are linked, therefore you can discuss religion on a science forum as you see fit. Your argument rests on your own definitions of science, of politics, of playing nice. You also twist others' words to mean what you wish. (Who knows what your students will be capable of.)

Under such conditions debate is impossible. So I'll use the "Ignore this user" button and see if it gets me away from the constant nagging. I doubt you care, I doubt my arguments will change your mind, but maybe there's the small possibility you will give everyone else a break.

To anyone else who read this far: I hope you forgive my outburst. I did spend a very long time considering it, if that's any consolation. If anyone thinks I'm over reacting, my apologies - I'm not offended by religion, I am offended by blatant disregard for others' feelings, and anyway it's only one forum and it's just my loss in the end.


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Otto Piechowski
Pooh-Bah


Reged: 09/20/05

Loc: Lexington, KY
Re: Sending humans to Mars actually feasible? new [Re: Ravenous]
      #5989742 - 07/25/13 02:58 PM

Ravenous,

First of all, I thank you for responding to my response to another’s post and attempting to correct my errors in logic, and inappropriate behaviors. Sincerely.

I would like to discuss with you a few of your comments, in part to understand better what you were saying, in part to correct what I see to be factual errors, and in part to create a dialogical partnership.

“The rules do not apply to you.” Did you mean that descriptively or prescriptively (as in “You don’t think the rules apply to you, do you?)

“You are a philosopher, an intelligent one at that” I am only a student and teacher of philosophy (one of the hats I’ve worn), but am most definitely not a philosopher. I think being a philosopher is a great thing, but I don’t think I reach that plateau.

Now, for an important criticism of yours, “[You, Otto] redefine words to mean whatever you wish in defence of your argument.” Please, sincerely, please be so kind, should you choose to communicate with me, to show me what you consider to be my redefinition of words. I can be blind in my assertions and have in fact been caught in just such a thing and have appreciated when others do me this kindness.

“(Who knows what your students will be capable of.)” Would you like to see the unsolicited voluntary (no strings attached) comments given me by my students over the years?

“I doubt you care, I doubt my arguments will change your mind, but maybe there's the small possibility you will give everyone else a break.” I do care. Specifically, I do not wish to harm people and would appreciate any help you can give me to avoid that. However, I also believe it is helpful to speak truth to power. In this forum power is represented by those who wield the power of censorship and the chorus of voices which support authority in the wielding of that power. Both authority and the choral function are very valuable and necessary in communities. Assuming you agree with me that speaking truth to power is a good thing, all that remains is for me to be helped by persons, such as yourself, when it is clear that what I think is a truth, is not.

“To anyone else who read this far: I hope you forgive my outburst. I did spend a very long time considering it, if that's any consolation. If anyone thinks I'm over reacting, my apologies”

I don’t think what you wrote was an outburst. I think it is authentic feeling and reaction. I do not think you are over-reacting.

“I am offended by blatant disregard for others' feelings, and anyway it's only one forum and it's just my loss in the end.”

I really don’t think I intend to hurt feelings. Now, it happens that persons, such as you and I, become so attached to ideas which control their very lives that when those ideas are challenged, they experience a visceral hurt. I often agonize over pushing the envelope; what is not appropriate and what is necessary. I try to formulate rules to act by to be as careful as possible. One of which is, for example, I don’t play the philosophy/theology card unless someone else makes a direct reference to philosophical/theological matters, or when a scientific assertion is made which is dependent on philosophical or metaphysical assumptions.

To be less wordy, when others touch on things philosophical, theological, political, metaphysical, I attempt to invite a dialogue.

Hope to hear from you.

All the best,

Otto

PS I attempted to send this communication by the private message to sender function available here on CN but was told you are not receiving private communications.


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Otto Piechowski
Pooh-Bah


Reged: 09/20/05

Loc: Lexington, KY
Re: Sending humans to Mars actually feasible? new [Re: Jarad]
      #5989746 - 07/25/13 03:00 PM

Jarad, is gravity gravity by whichever way it, gravity is formed?

I mean is the "gravity" which comes from a planet weighing (whatever the weight of the earth is) creating a gravity of, let's call it "1"; is that gravity the same as the artificial gravity created by a spinning space station creating a gravitational effect of "1"?

Otto


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Jarad
Postmaster
*****

Reged: 04/28/03

Loc: Atlanta, GA
Re: Sending humans to Mars actually feasible? new [Re: Otto Piechowski]
      #5989848 - 07/25/13 03:54 PM

Quote:

I often agonize over pushing the envelope; what is not appropriate and what is necessary. [snip]

To be less wordy, when others touch on things philosophical, theological, political, metaphysical, I attempt to invite a dialogue.




We understand your intention, Otto, but would appreciate it if you could try to avoid pushing the envelope here. We have made it abundantly clear where the line is, please try to resist going over it. If you see someone else approaching the line, don't feel the need to jump over it with them. You can initiate dialogue on those topics via PM.

Jarad


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Jarad
Postmaster
*****

Reged: 04/28/03

Loc: Atlanta, GA
Re: Sending humans to Mars actually feasible? new [Re: Otto Piechowski]
      #5989858 - 07/25/13 04:00 PM

Quote:

Jarad, is gravity gravity by whichever way it, gravity is formed?

I mean is the "gravity" which comes from a planet weighing (whatever the weight of the earth is) creating a gravity of, let's call it "1"; is that gravity the same as the artificial gravity created by a spinning space station creating a gravitational effect of "1"?

Otto




Gravity from centrifugal or centripetal force isn't quite the same as gravity from a planet, but for the purpose we are talking about (maintaining human bone density and muscle tone on a long voyage), it's close enough.

The larger the radius of the spinning motion is, the closer the gravity will be to what we experience here on earth. The centrifugal force is directly proportional to the radius, so for a small radius there will be significantly different force on your head from your feet. The larger the radius, the less those differences become and more like "normal" gravity it will feel. That's the reason for the tether idea - you can make a large radius without requiring a huge, massive ship.

Jarad


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Otto Piechowski
Pooh-Bah


Reged: 09/20/05

Loc: Lexington, KY
Re: Sending humans to Mars actually feasible? new [Re: Jarad]
      #5989865 - 07/25/13 04:05 PM

Jarad,

Again, your explanation is clear and, I think, correct.

follow up question: I have heard that some think there may be a subatomic "particle" associated with gravity, called gravitons. If that is the case, then is the gravity of a heavy body (e.g. the earth) the same as the gravity of the large spinning space station?

Otto


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WaterMasterAdministrator
Moat Keeper
*****

Reged: 02/17/10

Loc: Southeast Idaho, USA
Re: Sending humans to Mars actually feasible? new [Re: Otto Piechowski]
      #5989884 - 07/25/13 04:14 PM

Quote:

... is the gravity of a heavy body (e.g. the earth) the same as the gravity of the large spinning space station?




In a spinning space station, the inhabitants are not experiencing gravity, but rather centrifugal force.


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Jarad
Postmaster
*****

Reged: 04/28/03

Loc: Atlanta, GA
Re: Sending humans to Mars actually feasible? new [Re: WaterMaster]
      #5989913 - 07/25/13 04:36 PM

It's not exactly the same. The gravity we feel on earth is because the earth's mass is curving local space/time. This is another area where Danny is probably a better person to ask than me if you want to get into real detail.

In the case of a spinning space station, space/time is not being curved. You are moving, and the floor of the space station is pushing up against your feet changing your direction of motion from a straight line to a curve.

Mechanically, both result in force pushing down your body, putting stress on your bones and muscles. That's good enough for the purpose we want here.

At the more detailed level, the force on your body on earth is proportional to r^2, where R is the distance to the center of the earth. Since we are pretty far from the center of the earth, the difference between your head and feet is pretty miniscule.

On a spinning space station, it will be proportional to R, where R is the distance to the center of rotation. Since that is likely to be a lot smaller than the earth, the difference between your head and feet is likely to be noticeable. Also, the direction of "down" will change pretty quickly as you move around the station. So it will probably take some getting used to. Learning how to play "catch" with a ball on a rotating station would be rather challenging - it won't travel the same line it would here on earth, and the line will be different if you throw into the spin, against the spin, or across the spin. The force also depends on the square of the rotation rate, so you will "weigh" more if you run spinward, and "weigh" less if you run anti-spinward.

Jarad


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Otto Piechowski
Pooh-Bah


Reged: 09/20/05

Loc: Lexington, KY
Re: Sending humans to Mars actually feasible? new [Re: Jarad]
      #5989917 - 07/25/13 04:39 PM

Thanks Jarad.

Danny! (Other hard core physicist types). If gravitons are real, whatever they are, are they present, just as present, of the same type in the gravity well of a planet and the "gravity" of the space station both effecting the same gravitational effect/feeling on the human body?

Otto


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Ira
Carpal Tunnel
*****

Reged: 08/22/10

Loc: Mitzpe Ramon, Israel
Re: Sending humans to Mars actually feasible? new [Re: Otto Piechowski]
      #5990057 - 07/25/13 06:19 PM

Imperial College London has a plan. Behold, nothing up my right sleeve...nothing up my left...

http://news.cnet.com/8301-17938_105-57595403-1/how-to-get-to-and-from-mars-a-...

/Ira


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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: Sending humans to Mars actually feasible? new [Re: Jarad]
      #5990095 - 07/25/13 06:44 PM

Quote:

Seems to me that it would make sense to design the next LEO space station to rotate and generate artificial gravity as a test bed.

Jarad




The one up there now is modular, is it not? Just send up a long cable on the next Russian launch, split it in two and start the pieces spinning; might as well get some useful science out of the thing.

The only good reason that I could see to do that one was to keep Russian missile builders off the black jobs market.

Why would we think about building another? Or am I wrong, and we've gotten significant science out of it? More Teflon, or was it Tang?

Unless NASA is hiring me to work on it; in that case I'm all for it. A friend of mine got fired for incompetence while managing a Chik-Fil-A store in Houston, and got a job at NASA as a procurement officer; he's bought billions of dollars of stuff, says it's lots of fun, says the fast-food job was too hard.


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ColoHank
Carpal Tunnel
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Reged: 06/07/07

Loc: western Colorado
Re: Sending humans to Mars actually feasible? new [Re: Jarad]
      #5990179 - 07/25/13 07:46 PM

Quote:

Mechanically, both result in force pushing down your body, putting stress on your bones and muscles. That's good enough for the purpose we want here.





I wonder... is that conjecture or fact? I should think we won't know for sure until we test it over a long term in an otherwise weightless environment.


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llanitedave
Humble Megalomaniac
*****

Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Sending humans to Mars actually feasible? new [Re: ColoHank]
      #5990453 - 07/25/13 11:08 PM

Relativity considers the force due to gravitational acceleration and the force due to velocity acceleration to be exactly equivalent. Centrifugal force,as Jarad states, will create slightly different affects due to the "tidal" qualities of the limited rotational radius, but at any instantaneous time and location, it will still be exactly the same as gravity. You might be able to tell whether your feet are slightly heavier than your head, but then you can always lie down until the feeling goes away!

Biologically, it should be far superior to weightlessness.

As for attaching a tether to the ISS and swinging it around, I doubt that it will be a good idea. The ISS wasn't designed to withstand any significant torques. You'd need a vessel built with the capability in mind.


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Rick Woods
Postmaster
*****

Reged: 01/27/05

Loc: Inner Solar System
Re: Sending humans to Mars actually feasible? new [Re: derangedhermit]
      #5992947 - 07/27/13 12:39 PM

Quote:

Quote:

Seems to me that it would make sense to design the next LEO space station to rotate and generate artificial gravity as a test bed.

Jarad




The one up there now is modular, is it not? Just send up a long cable on the next Russian launch, split it in two and start the pieces spinning; might as well get some useful science out of the thing.




Ahh, why start now?

Quote:

The only good reason that I could see to do that one was to keep Russian missile builders off the black jobs market.

Why would we think about building another? Or am I wrong, and we've gotten significant science out of it? More Teflon, or was it Tang?

Unless NASA is hiring me to work on it; in that case I'm all for it. A friend of mine got fired for incompetence while managing a Chik-Fil-A store in Houston, and got a job at NASA as a procurement officer; he's bought billions of dollars of stuff, says it's lots of fun, says the fast-food job was too hard.




Wow! Now that's interesting! You could take that in a couple of completely different ways...


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Rick Woods
Postmaster
*****

Reged: 01/27/05

Loc: Inner Solar System
Re: Sending humans to Mars actually feasible? new [Re: ColoHank]
      #5992962 - 07/27/13 12:46 PM

Quote:

Quote:

How about this one; let's assume the Red Planet (movie) thesis is true, that we are killing the earth and will make it effectively uninhabitable in a few generations; is it realistically possible to terraform Mars? And, is it possible to terraform Mars in a time span of benefit to us who are, hypothetically speaking, killing the earth?





No and no. There's nowhere near enough gravity on Mars to sustain an atmosphere capable of supporting human life. Mars also has a weak and incoherent magnetic field, so what little atmosphere it has is vulnerable to further stripping by the solar wind, and its surface is bombarded by cosmic radiation. Not a very friendly place.




Theoretically, Mars could be terraformed, but: It would take a thousand years or more; it would require a lot of new technology that hasn't been developed yet (but could be); and the real kicker, the final product would only be temporary for the reasons Hank gave.

Anyone who thinks that, when we've finished trashing Earth, we can terraform Mars and go live there, is seriously deluded. Dangerously deluded, if they happen to be in a position of power where such fantasies could affect decision making.


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FirstSightModerator
Duke of Deneb
*****

Reged: 12/26/05

Loc: Raleigh, NC
Re: Sending humans to Mars actually feasible? [Re: HiggsBoson]
      #6005365 - 08/03/13 08:45 PM

Quote:


While it would be fun to go, I am unable to articulate a compelling business case that would convince a nation that the science value of this mission would be worth the cost.




A manned trip to the moon made no more "compelling business case" back in the 1960s than a manned trip to Mars does in the 2010s or 2020s, beyond the competitive national pride and prestige in the potential accomplishment. Yes, we got some moon rocks back for analysis from the Apollo missions, but now that we've advanced remote robotic capabilities in the 40 years since the manned lunar missions, that original advantage is vastly less compelling for any similar goal of returning some Martian samples to Earth. Better yet, we've advanced remote analysis capabilities to the point where even that is less compelling, though still useful (since the variety of testing possible on Earth is broader and more flexible than the limits of what we're able to send along with the spacecraft).

There's really no compelling "business case" for ANY manned mission to ANY of the planets, beyond that which existed for the original quest to land a man on the moon. The quest is more like mountain climbing in its fundamental goal: because it's there.


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